a. Field of the Invention:
The present invention relates to a tomographic apparatus.
B. Description of the prior art:
In general, a tomographic apparatus is intended to obtain tomograms of an object in which the required region is sharply imaged and the other parts are blurred, by moving an X-ray tube and a film about a certain point of the object while maintaining a certain positional relationship between them. From an ideal point of view, the X-ray tube and the film should at all times move in a path of movement best suited for an individual region of the object, but this is extremely difficult. In practice, most of paths of movement required are satisfied by a straight line, a circle, an ellipse, a hypocycloid and a spiral.
U.S. Pat. No. 3,770,955 discloses a tomographic apparatus capable of the aforesaid movement. In this apparatus, the X-ray and the film are supported by a link means which is driven by a cam-controlled hydraulic system. In this case, a highly trained operator is needed to handle such a hydraulic system.
On the other hand, mechanical means for controlling the movement of the X-ray tube and the film has been already disclosed in Japan patent application Publication Sho 38-1254 (publication date: Feb. 20, 1963), Japan Utility Model Laying-open Publication Sho 49-80,676 (laying-open date: July 12, 1974) and Japan Patent Laying-open Publication Sho 48-19,189 (laying-open date: Mar. 10, 1973). Those mechanical means fundamentally have an advantage of easy maneuvering, but a change or selection of the path of movement is still complicated and not substantially developed, as compared with the hydraulic means. At present, an apparatus of this kind is marketed under the tradename POLYTOME.